We’re getting taller and heavier. That’s not good news for food security or the planet

Humans aren’t just growing in number; we’re also getting taller and heavier–and these physical changes are set to threaten food security and make a bigger impact on the planet as our enlarging bodies require more food.

These are the findings of a recent Sustainability study, which makes the case that it’s not enough to consider the planetary impact of a growing population, alone. We should also recognise that increases in humanity’s height and weight are directly correlated with increases in the amount of food we consume–and thus, influence global food security and our environmental footprint, too.

The study found that between 1975 and 2014, human mass across the planet increased by 146%. On average, individual humans grew 14% heavier, and 1.3% taller. Overall, the growth of the planet’s population and its increasing mass over this 40-year period resulted in a 129% rise in global food demand. “From a global perspective, the effect of this additional demand is equivalent to the food energy needs of 286 million adults today,” the researchers write. For perspective, that surge in consumption is equivalent to the amount of food that would be needed to feed double the current population of Brazil.

The researchers explain that the majority of this 129% increase could be explained simply by the effects of more people on the planet. But when the impact of physical traits like weight and height were isolated, they found that these accounted for a striking 15% of the surge in food demand since 1975. This was offset slightly by a globally aging population: because older people tend to consume less food, that reduced demand–but only by 2%. So ultimately, 13% of the increase in food demand over the past four decades is attributable solely to humanity’s increasing height and weight.

What’s especially surprising is how quickly this change has occurred. It’s estimated that global weight has gone up by 146% since 1975–that’s the same as 39.68 metric tons, two times the mass of all the adults in the United States. Globally, maximum average weight has gone up from 57 kilograms to 65 kilograms in 40 years. And it’s estimated that height has increased by 20 cm in some parts of the world over the course of just four generations. (Increases in height track with greater availability of nutrients.) In terms of how this has altered food consumption, the average human is now consuming 15% more than we were in 1975, the study found.

Unfortunately, this 40-year-long trend will likely continue into the future, the researchers say. In fact, they estimate that feeding the nine billion people who will be on the planet in 2050 will need more calories than would be required to feed that same number of people right now–simply because humanity’s weight and height will continue to climb in the future, and with it, the demand for food.

To get their results, the researchers modeled humanity’s resource use according to multiple changing variables–height, weight, age, and sex–that were mapped to the populations of 186 countries over time. For information on food consumption they used data from the United Nations Food and Agriculture Organisation.

The paper doesn’t make dietary recommendations for saving the planet or feeding more humans. Rather, the authors emphasize, their key point is that food security and impact estimates fall far short of what they should be.

So, if we’re going to realistically grasp future food needs, we need to factor in the surprisingly large effect that humanity’s collectively changing body shape exerts on the very planet on which it depends.